(1) Field of the Invention
The present invention relates to a digital television, and particularly to a terminal that is equipped with a plurality of processing devices such as video recorder.
(2) Description of the Related Art
On the hardware of a broadcasting receiving apparatus represented by a television and a STB, a plurality of devices with different functions are interconnected so that an output from one device serves as an input to another device. By forming a series of flows in the above manner, a plurality of devices provide a great functionality on the hardware. For example, when video and audio are outputted to the screen of a digital broadcasting receiving apparatus, the following devices are connected on the hardware in order of mention, so that video and the like is displayed on the screen and audio is outputted by such devices performing the respective functions: a “tuner” that receives an broadcast signal as an input, performs filtering on such broadcast signal using the frequency as a key, and outputs an MPEG2 (Motion Picture Expert Group-2) transport stream; a “TS decoder” that receives the MPEG2 transport stream as an input, selects desired video/audio and data from it, and outputs video/audio data or data to be carried by TS packets corresponding to the selected video/audio data or data; an “audio decoder” and a “video decoder” that decode the video/audio data transmitted from the TS decoder and output it in a form that can be displayed on the screen; and a “display device” that synthesizes video and others indicated by the “video decoder” or the CPU.
In some cases, a broadcasting receiving apparatus such as above is equipped with more than one device of the same type. For example, when there are a plurality of “tuners” and “video decoders”, it is possible to decode more than one piece of video data concurrently and therefore to achieve a function, known as “Picture In Picture (hereinafter referred to as PinP)”, for displaying two types of video data concurrently, for example. In the case such as above where a plurality of devices of the same type exist, which “tuner” and which “video decoder” are to be interconnected cannot be determined freely. Therefore, it is usually determined beforehand that a specified “tuner” and a specified “video decoder” should be interconnected, and a series of devices are handled in “sets”. As a representative example method of using each device in such a case, a technique disclosed in “Japanese Laid-Open Patent application No.8-289220” is introduced here. In this invention, two sets of a “main tuner”, a “main video decoder”, an “insertion tuner” and an “insertion decoder” are used, and in the case of PinP display, the use of the “insertion tuner” makes it possible for the video and audio of a candidate selection to be displayed on a specified area on the screen, with an already-selected video and audio remaining displayed on the screen in full size.
In Europe, a specification known as “DVB-MHP (Digital Video Broadcasting-Multimedia Home Platform ETSI TS 101 812 V1.2.1 (2002-06)) for executing services on broadcasting receiving apparatus is defined and in operation. Meanwhile, in the United Sates, a specification called “OCAP (OpenCable Application Protocol OCAP1.0 Profile OC-SP-OCAP1.0-I07-030522) is under development on the basis of the DVB-MHP specification and scheduled to be brought into operation within the year 2005. Furthermore, similar specifications are under development or in operation in various countries. Broadcasting receiving apparatuses compliant with these specifications on service execution are capable of executing programs that are obtained from broadcast signals by means of download and the like. Representative examples of the programs include game and EPG (Electronic Program Guide) application.
As a service to be executed on a broadcasting receiving apparatus, it is natural to conceive an application for displaying more than one piece of audio and video data concurrently on one screen such as the aforementioned PinP and enhanced EPG. In order to output plural pieces of video and audio data concurrently on one screen, it is necessary to control sets of plural devices, as represented by the above-described patent. However, the DVB-MHP/OCAP specifications do not provide descriptions about the configuration for controlling sets of plural devices.